A thermal stress index
of a geographic location over a period of time can provide knowledge of overall
climate perceptible to the general public. Out of the three approaches to
assessing thermal comfort namely, rational, empirical and direct, the direct
approach is being used in the present study because of easy availability of all
inputs and reasonable comprehension of the assessments. Assessment and ranking
of cities using this approach based on the percentage of comfortable hours
alone may however be erroneous and misleading as this approach does not
consider the percentages of uncomfortable classes which could often be
substantially high. The modified approach for thermal comfort classification
demonstrates cumulative representation of all classes of thermal comfort
including uncomfortablity and provides relative ranking of cities. Analysis of
the results is presented here for five megacities (Delhi, Mumbai, Chennai, Kolkata
and Hyderabad) representing varying geographical and climatic locations of
India. These cities are ranked based on the routine and modified approaches and
results are discussed in detail on monthly, seasonal and annual average basis.
When the cities are compared only on the basis of comfortable hours, the
decreasing order of comfortability is Hyderabad, Kolkata, Delhi, Chennai and
Mumbai. However, considering the second methodology, it is revealed that the
contribution of uncomfortable hours is greater in Kolkata and Chennai in
comparison to Mumbai. The proposed methodology could be an improvement over the
current practices and provides a more rational method for relative ranking of
cities that could be used for tourism and energy demands.

S. Toy and S. Yilmaz, “Evaluation of Urban-Rural Bioclimatic Comfort Differences over a Ten-Year Period in the Sample of Erzincan City Reconstructed after a Heavy Earthquake,” Atmósfera, Vol. 23, 2010, pp. 387-402.